Ventura L, de Faria e Sousa S J, de Castro J C
Instituto de Física de São Carlos (USP), Grupo de Otica, São Carlos (SP), Brazil.
Phys Med Biol. 1998 May;43(5):1303-16. doi: 10.1088/0031-9155/43/5/018.
An automatic and objective system for measuring ocular refractive errors (myopia, hyperopia and astigmatism) was developed. The system consists of projecting a light target (a ring), using a diode laser (lambda = 850 nm), at the fundus of the patient's eye. The light beams scattered from the retina are submitted to an optical system and are analysed with regard to their vergence by a CCD detector (matrix). This system uses the same basic principle for the projection of beams into the tested eye as some commercial refractors, but it is innovative regarding the ring-shaped measuring target for the projection system and the detection system where a matrix detector provides a wider range of measurement and a less complex system for the optical alignment. Also a dedicated electronic circuit was not necessary for treating the electronic signals from the detector (as the usual refractors do); instead a commercial frame grabber was used and software based on the heuristic search technique was developed. All the guiding equations that describe the system as well as the image processing procedure are presented in detail. Measurements in model eyes and in human eyes are in good agreement with retinoscopic measurements and they are also as precise as these kinds of measurements require (0.125D and 5 degrees).
开发了一种用于测量眼屈光不正（近视、远视和散光）的自动客观系统。该系统包括使用二极管激光器（波长λ = 850 nm）将一个光靶（一个环）投射到患者眼底。从视网膜散射的光束被送入一个光学系统，并由一个电荷耦合器件探测器（矩阵）分析其聚散度。该系统在将光束投射到被测眼睛中时采用了与一些商用验光仪相同的基本原理，但在投影系统的环形测量靶以及检测系统方面具有创新性，其中矩阵探测器提供了更宽的测量范围，并且光学对准系统更简单。此外，处理来自探测器的电子信号也无需像普通验光仪那样使用专用电子电路；而是使用了一个商用图像采集卡，并开发了基于启发式搜索技术的软件。详细介绍了描述该系统以及图像处理过程的所有指导方程。在模型眼和人眼中的测量结果与视网膜检影测量结果高度一致，并且它们也达到了这类测量所需的精度（0.125D和5度）。
